The present invention relates to the retention of a heat shield in a sealed scroll compressor by creating a bias force on the heat shield.
Modern refrigerant compressors are typically contained within a sealed shell. The compressors are frequently divided into two compartments, a discharge chamber and a suction chamber.
A scroll compressor is one common type of sealed compressor. In a scroll compressor an orbiting scroll and a non-orbiting scroll each have a base, with generally spiral wraps extending from the bases. The orbiting scroll and the non-orbiting scroll are placed together such that the wraps create compression chambers. A shaft connected to a motor drives the orbiting scroll. As the orbiting scroll orbits the volume of the compression chambers is decreased.
Refrigerant is compressed in the chambers and discharged into the discharge chamber through a discharge port located in the non-orbiting scroll. The refrigerant may reach high temperature within the discharge chamber.
Historically, a thick separator plate isolated the discharge chamber from the base of the non-orbiting scroll. More recently, scroll compressor designs have attempted to eliminate the separator plate.
However, without a separator plate the refrigerant in the discharge chamber comes into contact with the base of the non-orbiting scroll. The refrigerant heats the base and consequently the compression chambers, which costs efficiency. A relatively thin heat shield has been placed extending about the base of the non-orbiting scroll. Due to the operation of the scroll compressor, there are pressure and temperature differences on each side of the heat shield. The pressure and temperature differences may create vibration and flexing of the thin heat shield.
One other concern is the heat shield may need to have openings, such as to allow flow from a pressure relief valve. In the past this has required that the heat shield be precisely aligned within the compressor such that the opening in the heat shield is aligned over the pressure relief valve to facilitate flow.
In embodiments of this invention a heat shield is associated within the base of a non-orbiting scroll. As known, the heat shield provides a barrier to insulate the non-orbiting scroll from the hot refrigerant in the discharge chamber. To address the above mentioned concern the heat shield is held at a deformed position such that a bias force resists flexing or vibration.
In a preferred embodiment a groove is placed in a boss surrounding a discharge port in the non-orbiting scroll. The heat shield is deformed into the groove. In a free state, the heat shield has a disc like appearance. An opening in the center of the heat shield is received over the boss. The heat shield is placed on the boss and pressed down. Essentially there is an interference fit between the heat shield and the boss. This fit deforms the heat shield away from its free curved shape creating a spring pre-load. The bias force from the deformation keeps the heat shield in position resisting flexing or vibration.
Preferably the inner edge of the heat shield is held in position in a groove located in the boss. The groove may have several different configurations. In the preferred configuration the bottom side of the groove is flat with a radius at the corner. The edge extends upward and is angled slightly toward the outside of the scroll. The angle prevents the heat shield from moving out of the groove.
In another embodiment the groove can be square cut. This groove has a distinct bottom, side, and top portion. This groove provides good support from the top when holding the heat shield in place. A third embodiment includes an angled groove, which has only two sides. The bottom side of the groove is flat, and a side extends upwardly and outwardly.
An alternative to having a curved heat shield is an embodiment where the outside edge of the heat shield is turned upward. The outside edge contacts the upper end cap when installed, deforming the heat shield when the end cap is secured to the compressor housing. This contact creates a downward bias force on the heat shield. Again, the bias force resists flexing and vibrating of the heat shield following installation.
In another embodiment, the heat shield is captured between the non-orbiting scroll and the outer housing. A portion of the heat shield is deformed when held at this captured position such that the bias force as mentioned above does occur.
One other aspect of the invention provides a heat shield, which more easily accommodates components such as a pressure relief valve. The valve requires a hole to be placed in the heat shield allowing the flow to pass through. One known heat shield is used with a non-orbiting scroll having ribs on a rear face, with pockets between the ribs. There is usually a hole in the heat shield through which the flow from the pressure relief valve may pass. However the single hole has needed to be aligned over the pressure relief valve. This aspect of the invention allows for the adjustments to be made in the alignment of the heat shield and the relief valve. In one aspect the hole aligned over the pressure relief valve can be a slot to allow for the valve and the heat shield to be slightly misaligned and still allow flow through the hole. There may also be a plurality of holes within an area of the heat shield, or a series of spaced holes in the heat shield. The holes may be off center within the heat shield again to allow for misalignment.